The present invention relates to a system for removing asbestos-containing materials (ACM) from buildings.
Since before the second World War through the early 1970's, as much as 300 million tons of asbestos mineral had been used in building construction in the United States. By the early 1970's, medical evidence began to establish that asbestos exposure can cause severe and irreversible lung damage and various forms of cancer. By the early 1980's, public concern over the hazards associated with asbestos became manifest in legislation which (1) limited the use of asbestos in new construction; (2) specified procedures for asbestos removal in buildings; (3) required removal of asbestos-containing materials prior to building remodeling or demolition; (4) required management of asbestos in schools.
The U.S. Environmental Protection Agency has estimated that about 45,000 schools and 73,000 public and commercial buildings contain some form of asbestos-containing materials (ACM). These ACMs are typically (1) surfacing materials sprayed or troweled onto ceilings and walls; (2) thermal insulation on pipes, ducts, boilers and tanks; (3) miscellaneous materials such as ceiling and floor tile and wallboards.
ACM removal is currently a heavily labor-intensive industry. Typically, surface ACM is removed by laborers using paint scrapers. The ACM is initially hand-wetted using sponges, low pressure water spray or the like, in order to reduce the amount of asbestos dust created during scraping. Thereafter, the ACM is scraped from its location in the building and allowed to fall to the building floor. Next, the dislodged ACM is shoveled up manually and placed in plastic bags. After the initial scraping of building surfaces with paint scrapers and the like, a final cleanup process is initiated to remove ACM from joints, crevices, beams, and other hard-to-reach areas in which large paint scrapers and the like are unsuitable. This cleanup process sometimes includes using pressurized water to blast the remaining ACM from its location on the building structure. Thereafter, all ACM, water, and other debris on the floor of the building is removed, typically by wet/dry vacuum units such as the type used in most shop and maintenance areas. As a final step, all surfaces of the building and enclosure are wiped down to remove any remaining ACM dust, etc.
Although regulations for asbestos removal vary from state to state, typically the area from which ACM is to be abated is required to be sealed off from the surrounding environment to prevent discharge of airborne asbestos fibers into the surrounding environment. During any period in which ACM removal is taking place, the sealed-off area within the building enclosure is required to remain at a negative air pressure with respect to the surrounding environment. The negative air pressure is typically provided by a "hepafiltered" vacuum source. "Hepafilter" refers to a filter which removes substantially all airborne particles having a particle diameter of greater than 0.3 microns. During asbestos removal, the air within the sealed enclosure is sampled on a regular basis to determine the density of airborne particles within predetermined ranges. Workers within the enclosure are required to wear approved protection gear having a hierarchy based upon the airborne particles within the building enclosure. In order to reduce costs associated with the more expensive protection gear, most contractors attempt to reduce airborne particle concentrations within the enclosed ACM removal area to a minimum, typically by providing a replenishing air flow which replaces the air within the enclosure on the order of four times per hour.
In order to prevent asbestos particles contained on the workers clothing and body from entering the atmosphere outside of the enclosed area, a triple air lock is typically provided at the entrance to the enclosed area. In the first area of the triple air lock positioned adjacent to the enclosed area, workers remove their protective gear and clothing, generally depositing it in sealed receptacles which are later removed from the area and cleaned or destroyed. After disrobing, a worker enters an intermediate area of the triple air lock which contains a shower. Each worker showers in this area and then progresses to the third area of the triple air lock in which clean clothes, etc., are provided. The water from the intermediate air lock shower is filtered to a particle size permissible for discharge into the surrounding sewer system, or ground water environment, typically 5 microns. In some cases, water which has been vacuumed from the floor of the enclosed ACM removal area by wet-vacuum in the final stages of cleanup is dumped into the worker's shower for filtering by the shower filter system. However, in most cases, the wet-vacuum container contains enough large ACM particles to prevent use of the shower as a filtering system, in which case all of the water and particles contained in the wet-vacuum are transferred to a barrel or other sealed receptacle for removal to an approved disposal site or for subsequent filtering. Due to the labor, dump fees, and inconvenience associated with removing large quantities of contaminated water to an asbestos disposal site, the use of water in ACM removal is minimized. Generally, blast spray water, when used at all, is applied at relatively high pressures, e.g. 5,000 psig or more, to decrease the total volume of water needed in any blast spray removal operations. The use of large amounts of water also damages underlying building structure such as floors and ceilings and has thus also been minimized to prevent unnecessary damage to the building.